The effect of activated sludge treatment and catalytic ozonation on high concentration of ammonia nitrogen removal from landfill leachate

• High concentration ammonia nitrogen removal from landfill leachate was achieved. • Catalytic ozonation converted nitrogen-containing organic matter into NH 4 + -N. • The aerobic denitrification played a key role in denitrification. • This technology provided a new way for the practical landfill leachate treatment. This study adopted the combination of activated sludge treatment and catalytic ozonation technology to efficiently remove the high concentration of ammonia nitrogen from landfill leachate. Through optimizing the parameters continuously, the COD, NH 4 + -N, UV 254 and colority respectively descended to 417.75 ± 6.72 mg/L, 9.77 mg/L, 1.98 ± 0.04 and 40 times, and 3D fluorescence also reduced significantly within 14 days. Target genes of AOB-amoA, nxrA, napA, nirS and nosZ analysis indicated that ammonia-oxidizing bacteria, nitrated bacteria, and denitrifying bacteria played a key role on nitrogen removal, aerobic denitrifying bacteria was dominated especially. The nitrogen removal process was as follows: catalytic ozonation converted nitrogen-containing organic matter into NH 4 + -N, then NH 4 + -N was converted into NO 2 – -N and NO 3 – -N with the action of ammonia oxidation, nitrification and catalytic ozonation. Finally, the denitrification microorganisms transformed NO 3 – -N or NO 2 – -N to N 2 . Therefore, this coupled process realized the nitrogen removal effectively from landfill leachate.